The present invention relates generally to barcode scanners, and, more specifically, to laser barcode scanners.
Common barcodes are used to identify certain information relating to an item or product to which they are affixed. A typical one dimensional (1-D) barcode includes a series of parallel lines and spaces of varying widths which in accordance with known conventions may be used to represent desired information relating to the item. A two dimensional (2-D) barcode provides more complex lines and spaces in two orthogonal axes for representing even more information regarding an item than is available in 1-D barcodes.
In either case, the barcodes must be optically read for decoding the information represented therein for subsequent use. Various barcode readers have been developed to decode the barcodes into multiple digit representations for inventory, production tracking, and for checkout or sales purposes, for example. Barcode scanners may either be fixed or portable, and therefore vary in complexity. Optical scanners must focus light for reading the barcodes, and variable distance reading also increases the complexity of the barcode scanner.
A simple type of barcode scanner includes a photodetector array known as a charge coupled device (CCD) which collects reflected light from the barcode to produce an image thereof which may then be suitably decoded in a processor. Either ambient light or light from light emitting diodes (LED), for example, may be used as the light source. Since these light sources have relatively low intensity, the typical CCD scanner is limited in resolution and cannot read a barcode any larger than the window of the corresponding scanning head, nor can it read barcodes at variable distances away from the window typically outside the range of about 1 and 1/2 inches.
Another type of barcode scanner uses laser light for the light source, which may be typically provided by conventional laser diodes. A laser barcode scanner enjoys the substantial advantage of significantly higher resolution than that of CCD scanners, with the ability to scan barcodes at substantially greater variable distances from the scanner window substantially greater than that of the CCD scanner. However, laser scanners are substantially more complex and expensive to manufacture than CCD scanners since they typically include suitable scanning optics for rastering the laser beam in sequential passes over the barcode at a suitable scanning frequency for decoding the barcode. Rastering is typically effected by using a rotating multi-faceted mirror which is inherently limited in speed.
For 1-D barcodes, conventional laser scanners are commonly available. However, 2-D barcodes require decoding in two orthogonal axes which increases the processing time of a typical laser scanner. Since typical laser raster scanners are inherently limited by the mechanical rastering speed thereof, it is desirable to have an improved laser scanner for decoding 2-D barcodes at increased speed and with the relatively high resolution and depth of field of laser scanners.